Presently the most cost effective power generation alternative for meeting our future electrical energy needs is the coal burning power plant. Nuclear power is not thought to be a cost effective alternative for the near future because of the high cost of construction. Additionally, hydro power is also not available for development in many areas of the country in significant amounts, and the cost of oil and gas fuels for electrical power generation have risen beyond competitive cost levels typical of base loaded generation. Thus, coal burning power plants have become the staple for electric generation, in spite of the high cost of pollution abatement.
A wood burning power plant is an environmentally and cost beneficial alternative technology. Growing trees for fuel is the purest and cleanest form of capturing and storing solar energy. Also, the source is domestic and 100% renewable. The largest power application using wood fuel in the United States is at the generating plant in Burlington, Vt.
However, the conventional wood burning power plant uses wood fuel processed to woodchips, shreds, pellets, dusts, powder and other forms. Because of the cost of processing trees into appropriate forms for the power plant, conventional wood burning electric generation cannot be competitive with other alternative energy sources for power generation such as coal, hydro and nuclear. Furthermore, such processed wood burns rapidly, frequently in suspension as it is injected into the furnace above the grates. In order to keep a constant and steady source of heat supplied to the boiler of the power plant, the processed wood must be supplied to the furnace at a precisely controlled rate.
One solution to the wood burning alternative is presented in Ostlie, U.S. Pat. No. 4,706,645 which is hereby incorporated by reference. There, substantially whole trees are relied upon as the fuel source. While reducing the costs associated with processing trees into appropriate forms for the power plant, the problem of supporting the substantially whole trees in the combustion chamber arises. Grates that support the trees in the furnace must be cooled to protect them from damage due to the high temperatures in the furnace. Water cooled grates for furnaces used to suspend solid fuel are typically made by casting, and are continually moving or traveling in the furnace. These grates were typically designed to support about six inches of solid fuel, and do not possess the strength to support a deep bed of whole trees nor can they accommodate the high pressures and flows typical of large steam generator furnaces.